JSP Error messages don't show when using Spring Data JPA - spring

Question

This is my repository:
#Repository
public interface ProductRepo extends CrudRepository<Product,Integer> {
public List<Product> findAll();
public Product findById(int id);
}
My Entity Bean:
#Entity
#Table(name = "product")
public class Product {
#Id
#GeneratedValue(strategy = GenerationType.AUTO)
#Column(name = "product_id")
private Integer id;
#NotEmpty
#Column(name = "product_name")
private String productName;
Controller:
#PostMapping("/add-product")
String addProduct(#Validated #ModelAttribute("product")Product product, BindingResult bindingResult){
if (bindingResult.hasErrors()) {
System.out.println("has errors: " + bindingResult.toString());
}
System.out.println( "adding Product ..." );
productService.save(product);
return "redirect:/products/success";
This is my view
<form:form action="add-product" method="post" modelAttribute="product">
<label for="productName">Product Name</label>
<form:input path="productName" id="productName" type="text" placeholder="Add product name"/>
<form:errors path="productName" />
...
It just works fine when using Hibernate SessionFactory to store to database, like this:
// A shorter way to save customer
Session currentSession = sessionFactory.getCurrentSession();
currentSession.saveOrUpdate(customer);
but when replacing it with Spring Data JPA, it starts throwing exceptions and return 500 html pages instead of just rendering the error field as it used to be.
There are 4 exceptions thrown:
javax.validation.ConstraintViolationException: Validation failed for classes [com.luv2code.springdemo.entity.Product] during persist time for groups [javax.validation.groups.Default, ]
List of constraint violations:[
ConstraintViolationImpl{interpolatedMessage='must not be empty', propertyPath=productName, rootBeanClass=class com.luv2code.springdemo.entity.Product, messageTemplate='{javax.validation.constraints.NotEmpty.message}'}
]
javax.persistence.RollbackException: Error while committing the transaction
org.hibernate.internal.ExceptionConverterImpl.convertCommitException(ExceptionConverterImpl.java:77)
org.hibernate.engine.transaction.internal.TransactionImpl.commit(TransactionImpl.java:71)
org.springframework.orm.jpa.JpaTransactionManager.doCommit(JpaTransactionManager.java:536)
org.springframework.transaction.TransactionSystemException: Could not commit JPA transaction; nested exception is javax.persistence.RollbackException: Error while committing the transaction
org.springframework.web.util.NestedServletException: Request processing failed; nested exception is org.springframework.transaction.TransactionSystemException: Could not commit JPA transaction; nested exception is javax.persistence.RollbackException: Error while committing the transaction
Previously, without using JPA, the validation error message shows in the view <form:errors />, not thrown as an exception with 500 http error code. What do I miss here?

Answer 1

The behavior you see has nothing to do with Spring Data JPA but the fact that you switched from plain hibernate (judging from your code snippets) to JPA.
When using JPA and using JSR-303 those will work together to prevent invalid entities from being entered in the database by throwing the validation exception. When using plain Hibernate this doesn't happen (at least the exceptions don't propagate).
Which was due to you have written your request handling method. In case of errors in the model you just do a System.out and happily continue the method, what you should have been doing there is return to the original view instead (I assume products/add-product).
#PostMapping("/add-product")
String addProduct(#Validated #ModelAttribute("product")Product product, BindingResult bindingResult){
if (bindingResult.hasErrors()) {
System.out.println("has errors: " + bindingResult.toString());
return "products/add-product";
}
System.out.println( "adding Product ..." );
productService.save(product);
return "redirect:/products/success";
}
Basically you failed at handling the case of errors properly leading to exceptions being thrown due to the JPA and javax.validation working in a united fashion.